As technology progresses, the manufacturing technique of monitor display is also progressing. After the technique of liquid crystal display (LCD), the newest technique of monitor display brought to the market is one that utilizes organic light emitting diodes (OLEDs). Each OLED requires a circuit to drive it to emit light. The light can be of either a single color, such as red, green or blue, or even multiple colors. The advantages of OLEDs are the flexibility, liberation from vision angle restriction, long product lifetime and low power consumption.
Each pixel of an active matrix OLED needs an OLED and a circuit. Therefore, there are ten thousands or even millions of circuits in one panel. It is a complicated task to test the normal functionality of all circuits in one panel. FIG. 1, FIG. 2 and FIG. 3 show the common circuits configured to drive OLEDs within monitor displays. Referring now to FIG. 1, FIG. 2 and FIG. 3, the method of prior art for testing these circuits is to enable each one via the write scan line WSL and to input a certain voltage level via the data line DL after OLEDs are implanted. The circuit transfers the voltage level into a current signal I which makes the OLED emit light. According to the voltage level, test engineers determine the OLED's functionality simply by observing its luminosity with eyes. Moreover, if a circuit fails the test, the OLED having been implanted in it is wasted and cannot be recovered even though the OLED itself may be perfect. Accordingly, this test method of prior alt would result in not only imprecision caused by the subjective decision of the test engineers but also high costs.